Airfoil vane



Feb. 20, 1968 R. H. KRAIMER ET AL 3,369,792

AIRFOIL VANE Filed April '7, 1966 INVENTOR. WIN/4M 2. 77/5004? 5&55277/ [am/5e United States Patent 3,369,792 AIRFOIL VANE Robert Henry Kraimer, Cincinnati, Ohio, and Wiliiam R.

Theodore, Belmont, Mass, assignors to General Electric Company, a corporation of New York Filed Apr. 7, 1966, Ser. No. 540,967 8 Claims. (Cl. 25339.1)

The present invention relates to a fluid directing element and more particularly, to airfoil vane structure employing hollow vanes with insert means for directing minimum fluid flow for adequate cooling of jet engine parts such as turbine diaphragms.

In present high temperature machine parts such as the turbine vane-s of jet engines, whether rotating or stationary, it is necessary to provide a cooling arrangement. It is possible to design engines that operate efliciently at gas temperatures much higher than the materials are able to withstand. Thus, adequate cooling schemes must be devised and structures designed which permit operation at elevated gas temperatures beyond the capacity of the material.

Various nozzle vane structures have been designed to permit the circulation of cooling fluids and adequately reduce temperatures. Typically, some designs employ cast-in passages wherein cooling fluids are circulated in a sinuous manner through the passages within the walls of the particular component such as a turbine bucket or vane. The problem with such designs is that the casting procedure becomes a difficult operation wherein the passages are formed by providing the transverse walls across the vanes as a part of the casting. This results in temperature gradients that produce thermal stress concentrations which often result in cracking and inadequate life. Also, the casting operation is diflicult and expensive.

More optimum structure for high temperature application has proved to be hollow designs that are either fabricated or cast. On thin wall designs or constructions, any suitable means, such as inserts, are provided to confine and guide the cooling fluid adequately to cool the desired parts of the vane exposed to the hot fluids. Generally, in such structures, the insert means acts as a baffle or guiding structure to direct the cooling fluid in a sinuous manner and discharge it after it has performed its cooling purposes. Of course, the maximum amount of cooling with the minimum amount of cooling fluid is desired and various internal structures have been proposed to achieve this end. It is customary to take the incoming fluid and direct it along the hot leading edge and move it towards the trailing edge and then use it to cool the trailing edge by transversely flowing it through or on one side or the other thereof and then discharging it into the cycle to avoid losses.

The main object of the present invention is to provide a fluid directing element in the shape of an airfoil vane for a turbine diaphragm wherein each vane is hollow and has insert means therein to guide cooling fluid, the insert mean-s being so formed to direct a minimum flow through passages within the vane in a highly eflicient manner.

Another object is to provide such a structure wherein the vane may be an easily cast structure adapted to support insert means which direct cooling fluid for maximum cooling with the minimum amount of fluid by an eflicient recirculating arrangement.

- A further object is to provide such structure wherein the internal insert means of the vane is an easily produced structure that slips into place to provide eflicient circulation of cooling fluid.

A further object is to provide such a structure wherein the insert means in the hollow vanes comprises several inserts that are shorter than the vane and are staggered and 3,369,792 Patented Feb. 20, 1968 easily held in position by the vane itself to provide a sinuous cooling flow arrangement to avoid thermal stresses.

Briefly stated, the invention provides a fluid directing element for turbomachinery in which the element is a hollow airfoil vane having leading and trailing edges. Forming part of the vane, which may be cast, are preferably two pairs of axially spaced and longitudinally extending ribs on opposite internal surfaces of the hollow airfoil. A pair of thin-walled generally U-shaped and longitudinally shorter insert means extend lengthwise of the vane internally thereof from one end of the vane. Each insert, which may be of sheet metal construction but is not limited to such material, has crimped surfaces on opposite legs of the U and spans a pair of the ribs whereby the insert may be slid along said ribs longitudinally into the vane to form a longitudinal baflie with a longitudinal passage between the inserts. Means are provided to limit the extension of the insert into the vane so that the shorter inserts are disposed to define cross passages at opposite ends respectively of adjacent inserts. Blocking means is proreverse the fluid flow and means are provided at opposite ends of the vane to permit fluid entry and exit. The

inserts are preferably disposed to form cooling passages adjacent the leading and trailing edges and the blocking means may comprise caps across the vane ends. Cooling means is also provided in the trailing edge to discharge fluid adjacent and transverse to the edge. The inserts may have tab means at their opposite ends to limit their extension into the vane.

While the specification concludes with the claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed the invention will be better understood from the following description taken in connection with the accompanying drawings in which:

FIGURE 1 is a perspective view of a typical nozzle segment of vanes as used in a turbine diaphragm,

FIGURE 2 is a cross sectional view through an individual vane of the invention, and

FIGURE 3 is a cross sectional view taken on the line 33 of FIGURE 2.

The present structure is described for convenience as one of the vanes of a turbine diaphragm structure but it will be appreciated that the specific structure described may have application elsewhere such as struts or other engine components such as airfoil-like structure requiring similar cooling capabilities.

Referring first to FIGURE 1, there is shown a single vane segment of a turbine diaphragm structure including outer band 10 and inner band 12 having nozzle vanes 14 between the bands. Vane 14 is hollow, as shown, and is a fluid directing element of an airfoil shape as is well known. Any number of vanes per segment may be employed or single vanes may be used in arrangements being known. FIGURE 1 is merely illustrative of a typical construction. It will be appreciated that a multiplicity of the vane elements in the segments of FIGURE 1 may comprise the turbine diaphragm structure that extends completely around an annulus downstream of a combustor in a jet engine and receives the hot combustor gases. Additionally, such nozzle vane elements may be employed as other stages in a multi-stage application. They direct the hot gases onto the rotating buckets, not shown, in the usual manner. Ease of assembly and lower cost construction has indicated that the diaphragm structure may conveniently be made in segments of multiple vanes or single vanes andthe segments can be cast with the individual nozzle vanes 14 therein. A multiplicity of such segments are then joined to form a circle.

'For adequate cooling of the individual vanes below the main gas temperature, it is necessary to use a fluid, such as compressor bleed in a gas turbine, or other suit-able fluid at a lower temperature than the exhaust gases. Referring to FIGURE 2, the bands may have upstream flanges 16 and downstream flanges 18 to abut the normal adjacent engine structure in the conventional manner. Similar flanges may be provided on the inner band 12 for supporting internal sealing structure in a known manner. To reduce costs and obtain high heat transfer coefficients for adequate cooling with the minimum amount of cooling fluid, it is possible to cast the whole structure shown in FIGURE 1 and bolt individual segments or vanes together as previously noted.

Reference is now made to FIGURE 2 showing a cross section of an individual fluid directing element or hollow airfoil vane 14. In the normal nozzle structure the hollow vane 14 is of airfoil shape and has leading and trailing edges 20 and 22 respectively. The airfoil shape provides a suction or convex surface 24 and a pressure or concave surface 26. In normal expected turbine operation, surface 24 is exposed to higher outside heat transfer coefficients than is surface 26 and therefore requires more internal cooling. Also, leading edge 29' is generally exposed to higher temperatures and requires more cooling.

Cooling fluid from a suitable source, such as compressor bleed, is brought to the individual vane means in any conventional manner. In order to distribute the fluid properly within the thin-walled vane, there is provided insert means which will be described. It is desired that the inserts be inexpensive and easily assembled by merely slipping into position to avoid the need for the cast-in cross ribs which are difiicult to provide.

In order to provide support structure, each of the cast vanes, as part of the casting, is provided with longitudinally extending ribs 26 that are disposed on opposite internal surfaces of the hollow airfoil and are preferably provided in pairs, as shown, directiy opposite one another as better seen in FIGURE 3. These ribs means extend from one end of the vane to the other as shown. In order to provide a battle or sinuous passage for the directing of cooling fluid, thin-walled generally U-shaped insert means 30 are provided. Preferably a pair of such insert means, as shown in FIGURE 3, are provided to clamp on each rib 28 as shown. The inserts are longitudinally shorter than the length of the vane as seen in FIGURE 2 and are staggered as will be further explained. The inserts extend lengthwise of the vane from one end and each insert has crimped surfaces 3-2 on opposite legs of the U. These surfaces are designed to span the ribs 28 and lock the insert in position as will be apparent. Additionally, the ribs then form a track whereby the insert may be slid along the ribs into the vane toform a longitudinal baffle, and where two inserts are used as shown in FIG- URE 3, a longitudinal passage 34 is thus formed between the inserts.

The longitudinal ribs 28 and insert means 30 are'preferably disposed inwardly from the leading and trailing edges as shown in FIGURES 2 and 3 to form longitudinal passages 36 and 38 immediately adjacent the leading and trailing edges respectively. By forming the inserts shorter than the longitudinal extent of the vane it will be apparent that cross passages 40 and 42 will be formed when the inserts are staggered as shown in FIGURE 2. In order to form these passages, the inserts may be inserted into the vane from one end and secured in position by having tab means 44 and 46 at respectively opposite ends of the inserts to provide the sinuous passage for the cooling fluid through the vane. Of course, any suitable locating means such as suitably secured tabs 44 and 46 may be used to position the inserts in the staggered position shown.

In order to provide for the reversal of the fluid to follow the cooling passages, cap means 48 and 50 are used as blockers across the vane ends and are disposed opposite the cross passages, as shown, whereby the fluid flow is reversed from one passage to the next.

For providing flow through the vanes, an inlet means 52 and exit means 54 are provided at opposite ends of the vane. It is generally desired to cool the trailing edge of the vane and to this end suitable apertures 56 are provided whereby the cooling fluid in the passage adjacent the trailing edge may exit transversely through apertures 56 as well as outlet 54. Thus, outlet 54 and apertures 56 may be metering means to determine the required amount of fluid for cooling. After exit from outlet 54 the fluid may be used elsewhere such as for sealing or use in other appropriate structure. The fluid discharging through apertures 5a is preferably adjacent and transverse to the trailing edge as shown in FIGURE 3 and may be on the suction side 24- as shown or it may be directed centrally out the trailing edge depending on the cooling requirements.

With the easily cast vane structure shown, and the longitudinal ribs 28, it will be apparent that the simple inserts may be slid into position and locked by the tabs to limit the extension of the inserts into the vane. This provide, in a very simple manner, an easily assembled structure for adequate cooling with minimum fluid. The U-shaped insert means may be spring-clips that are easily held in position as shown in FIGURE 3 and are insertable from one end such as the wide end when in a tapered vane as shown in FIGURE 2. A simple tack weld may be used to lock the inserts in position by their tabs directly to the caps 48 and 50 to provide a light weight highly efficient cooled vane as shown. This arrangement extracts maximum heat transfer capability out of minimum cooling fluid after which it may be used for other purposes. This results in a better engine cycle when used in a gas turbine engine since the least amount is being withdrawn from the cycle.

While there has been described a preferred form of the invention, obvious equivalent variations are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described and the claims are intended to cover such equivalent variations.

We claim:

1. A fluid directing element for turbomachinery comprising, a hollow airfoil vane having leading and trailing edges,

at least one pair of longitudinally extending ribs disposed on opposite internal surfaces of said hollow airfoil, said pair of ribs being spaced apart throughout their longitudinal length,

thin-walled generally U-sha-ped insert means extending lengthwise of said vane internally thereof from one end,

said insert having crimped surfaces on opposite legs of the U and spanning said ribs whereby said insert may be slid along said ribs into said vane to form a longitudinal baffle,

means on said insert limiting its extension into said vane, and

means on opposite sides of the baffle and at opposite ends of said vane for fluid entry and exit. 2. A fluid directing element for turbomachinery comprising, a hollow airfoil vane having leading and trailing edges,

at least one pair of longitudinally extending ribs disposed opposite each other on opposite internal surfaces of said hollow airfoil,

thin-walled generally U-shaped insert means extending lengthwise of said vane internally thereof from one end to form a longitudinal fluid passage adjacent said leading edge,

said insert having crimped surfaces on opposite legs of the U and spanning said ribs whereby said insert may be slid along said ribs into said vane to form a longitudinal baflie,

means on said insert at said one end limiting its extension into said vane,

inlet means adjacent said limiting means for admitting fluid to said longitudinal passage,

cap means spaced from said insert at its other end for permitting discharge of fluid from said longitudinal passage to the other side of the baflie,

and means in said trailing edge to discharge fluid adjacent and transverse to said trailing edge.

3. A fluid directing element for turbomachinery comprising, a hollow airfoil vane having leading and trailing edges,

at least one pair of longitudinally extending ribs disposed opposite each other on opposite internal surfaces of said hollow airfoil,

thin-walled generally U-shaped insert means extending lengthwise of said vane internally thereof from one end,

said insert having crimped surfaces on opposite legs of the U and spanning said ribs whereby said insert may be slid along said ribs into said vane to form a longitudinal baflie,

a tab on said insert for limiting its extension into said vane from said one end,

and means on opposite sides of the baffle and at opposite ends of said vane for fluid entry and exit.

4. Apparatus as described in claim 2 wherein said ribs are disposed opposite one another, and

said insert has tab means at one end thereof to limit its extension into said vane.

5. A fluid directing element for turbomachinery comprising,

a hollow airfoil vane having leading and trailing edges,

two pairs of axially spaced and longitudinally extending ribs disposed on opposite internal surfaces of said hollow airfoil,

a pair of thin-Walled generally U-shaped longitudinally shorter insert means,

each insert extending lengthwise of said vane internally thereof from one end,

each insert having crimped surfaces on opposite legs of the U and spanning a pair of said ribs whereby said insert may be slid along said ribs into said vane to form a longitudinal bafile with a longitudinal passage between the inserts,

means on each insert limiting its extension into said vane,

said shorter inserts being disposed to define cross pasages at opposite insert ends respectively,

blocking means at the vane ends opposite said cross passages to reverse the fluid flow, and

means at opposite ends of said vane for fluid entry and exit.

6. Apparatus as described in claim 5 wherein said inserts are disposed inwardly of said edges to form longitudinal passages adjacent said leading and trailing edges,

said blocking means comprising caps across said vane ends, and

means in said trailing edge to discharge fluid adjacent and transverse to said edge.

7. Apparatus as described in claim 5 wherein said pairs of ribs are disposed opposite one another and said inserts have tab means at respectively opposite ends to limit their extension in said vane.

8. Apparatus as described in claim 6 wherein said pairs of ribs are disposed opposite one another and said inserts have tab means at respectively opposite ends to limit their extension in said vane.

References Cited UNITED STATES PATENTS 2,647,368 8/1953 Triebbigg et al. 253-39.15 2,801,071 7/1957 Thorp. 2,801,073 7/ 1957 Sovage. 2,817,490 12/ 1957 Broffitt. 2,840,298 6/ 1958 Custle et al. 2,859,011 11/ 1958 Zimmerman. 2,866,616 12/ 8 Stalker. 2,873,944 2/ 1959 Wiese et al. 2,906,495 9/ 1959' Schum et al. 2,923,525 1/ 1960 Creek. 3,095,180 6/1963 Clark et al.

HENRY F. Primary Examiner. 

1. A FLUID DIRECTING ELEMENT FOR TURBOMACHINERY COMPRISING, A HOLLOW AIRFOIL VANE HAVING LEADING AND TRAILING EDGES, AT LEAST ONE PAIR OF LONGITUDINALLY EXTENDING RIBS DISPOSED ON OPPOSITE INTERNAL SURFACES OF SAID HOLLOW AIRFOIL, SAID PAIR OF RIBS BEING SPACED APART THROUGHOUT THEIR LONGITUDINAL LENGTH, THIN-WALLED GENERALLY U-SHAPED INSERT MEANS EXTENDING LENGTHWISE OF SAID VANE INTERNALLY THEREOF FROM ONE END, SAID INSERT HAVING CRIMPED SURFACES ON OPPOSITE LEGS OF THE U AND SPANNING SAID RIBS WHEREBY SAID INSERT MAY BE SLID ALONG SAID RIBS INTO SAID VANE TO FORM A LONGITUDINAL BAFFLE, 